World number 12 heading back to the practice court to "find his highest level" after knee surgery.

A disappointing start to the 2018 season for Stan Wawrinka continues after the three-time Grand Slam champion announced that he is withdrawing from both forthcoming ATP World Tour Masters 1000 events at Indian Wells and Miami.

Wawrinka was unable to defend his maiden US Open crown last summer due to a long-term left knee injury that required surgical intervention and ended his season early, and the Swiss has struggled since returning to the tour at the beginning of the year.

He was upset by American Tennys Sandgren in the second round of the Australian Open and suffered a shock defeat to qualifier Mirza Basic in the semi-finals of a 250 event in Sofia before being dumped out in the first round of the Rotterdam Open by world number 259 Tallon Griekspoor, clearing the path for compatriot Roger Federer to return to the top of the ATP rankings for the first time in more than five years.

Wawrinka was handed a bye through the first round of the Open 13 in Marseille last week before retiring hurt while trailing 6-4, 1-1 in the second set of his match against Ilya Ivashka of Belarus.

On Thursday [1 March], the 32-year-old confirmed that he would not be competing in either leg of the so-called Sunshine Double, meaning he will lose the 600 ranking points gained from reaching the final of the BNP Paribas Open at Indian Wells in 2017. As top seed in Miami, he was eliminated in the fourth round by Alexander Zverev in the fourth round.

"Unfortunately I need to announce that I won't be able to play in Indian Wells and Miami," Wawrinka said in a statement. "They are both amazing events but coming back from a big surgery is complicated and after having played a few tournaments I have discussed with my team that it is best for me to build on the progress and go back to practice.

"I've enjoyed being back on tour playing matches and this gives me even more motivation to go back on the practice court. My goal is to find my highest level again and in order to do that I will keep working hard every single day."

The 2015 French Open champion added that he was aiming to return to action in time for the clay-court season and the run-up to Roland Garros in May.

"I need to be patient and give my body the time it needs, but as of now my goal is to come back on clay. I love that part of the season and hope to be ready by then. I want to thank all my fans who are always a great support. I'm working hard on and off the court and hope to be back within a few weeks."

Wawrinka's announcement comes just two days after Rafael Nadal pulled out of the Mexican Open in Acapulco as a result of the recurrence of an upper leg injury that forced his retirement from the Australian Open quarter-finals in January.

The Spaniard subsequently stated that playing at Indian Wells would be a "great goal" for him, although insisted that now was not a time to "make drastic decisions".